Picking the top U.S. women’s marathoner of all time is as easy as it was to pick the top man.

It’s Joan Benoit Samuelson, of course.

(For my rankings of the Top 10 men, a list headed by Frank Shorter, click here.)

And picking the Top Ten women is as hard as it was to pick the Top Ten men – but for a very different reason.

While men’s marathoning spans more than a century and two distinct eras – before and after the emergence of East Africans who rule the sport – women’s marathoning at the elite competitive level is barely 30 years old.

The first Olympic marathon for women was in 1984. The first world championship race in 1983. Only in the 1970s did invitational marathons start to attract good women’s fields.

So the problem is lack of numbers among U.S. women with significant achievements, especially as East African women began to duplicate the success of their male counterparts.

The top two, Benoit and Deena Drossin Kastor, are in a league by themselves among U.S. women. A month from her 39th birthday, Kastor hopes to make her third Olympic marathon team with a top-three finish at Saturday's U.S. trials in Houston.

As with the men, Olympic performances trump everything in these rankings. Here are my other general criteria:

*Dominance of an era. You can beat only those runners competing with you, and doing so convincingly is a mark of greatness. There is no real way to compare 1966 or 1984 to 2011, so you judge each in its own context.

*Times. Even with dramatic differences between courses and weather conditions, a fast time is a historical calling card.

*Contribution to the sport. Some people not only have been great competitors with impressive results but also had a lasting and historically significant impact on either the public appeal of marathoning or the elite part of the sport.

The top women:

1. Joan Benoit Samuelson. Few knew of her when she entered the 1979 Boston Marathon, ran the course in a Red Sox cap and emerged the winner. Four years later, she won Boston again in a world-record time (predating the decision to disqualify Boston times from record consideration because of the course layout.) But it was 1984 that turned her into a running immortal: 17 days after arthroscopic knee surgery, Benoit won the Olympic trials. Three months later, she audaciously took off on her own after three miles of the inaugural Olympic women’s marathon and went on to win in a time (2:24:52) only three women have bettered in the Olympics (all in 2000). In 1985 at Chicago, against one of the top fields ever assembled for a women’s marathon, Benoit beat world record-holder Ingrid Kristiansen and two-time Olympic medalist Rosa Mota (the eventual 1988 Olympic champion) with a time, 2:21:21, that stood as the U.S. record until Deena Drossin Kastor broke it by five seconds in 2003. Benoit still has the No. 3, 6, 7 and 10 clockings (Boston included) on the all-time U.S. list and has been an indefatigable ambassador for her sport the past quarter-century.

2. Deena Drossin Kastor. She is the only U.S. woman ever to break the 2:20 barrier (2:19:36). The country’s only other female Olympic medalist, with a bronze at Athens in 2004. The only U.S. woman to win one of the country’s Big Three marathons (Boston, New York, Chicago) since 1994. The only U.S. woman to win the London Marathon. And owner of the first, second and fourth fastest times ever by a U.S. woman.

The indomitable Switzer turned a pioneering moment for women’s marathon into a career of advocacy for women’s involvement in elite and recreational sport. Five years before women were allowed official entry to the Boston Marathon, she entered the 1967 race under the gender-neutral name she used to sign documents and school papers: “K.V. Switzer.” When race official Jock Semple discovered her presence, he tried to throw her out. Pictures of their confrontation on the course got worldwide attention and became instant touchstones for women athletes. Switzer went on to win the New York Marathon in 1974, helped create a women’s running series with events in 27 countries and lobbied for including a women’s marathon in the Olympics.

Bobbi Gibb also played a key role, with less fanfare, in opening the marathon to women at a time when the longest women’s Olympic race was 800 meters. She was Boston’s first woman finisher, completing the race without having registered in 1966, when her unofficial time of 3:21 was better than two-thirds of the 500 men’s entrants. The home page of her web site has a photograph of the front page of the April 20, 1966 Boston Record-American, on which her achievement merited a giant headline reading, “Hub Bride First Gal to Run Marathon.” Befitting her low-profile personality, Gibb also ran sub-rosa in 1967 (beating Switzer by an hour) and 1968. In 1996, to mark the 100th anniversary of the Boston Marathon, Gibb was officially recognized as the women’s winner for those three years. She sculpted the trophies given to the first three finishers at the 1984 U.S. women’s Olympic trials.

5. Lisa Larsen Weidenbach Rainsberger: She is the last U.S. winner of the Boston Marathon (1985). The only U.S. woman to win two Chicago Marathons (1988-89). One of seven U.S. women with three or more marathons under 2:30. (When she did it the final time, in 1990, only Benoit had three or more sub-2:30s.) She also was the heartbreak kid, finishing fourth in three straight Olympic trials, thereby missing the Summer Games by one place each time. “This kind of bittersweet,” Weidenbach said of her first Chicago victory, which came a month after the 1988 Seoul Games. “Nothing can make up for not making the Olympics.”

6. Kim Jones. Her career was noteworthy for results, times and longevity. For more than a decade, Jones was among the best U.S. women; from 1986 through 1997, Track & Field News magazine had her No. 1 in the country in its annual rankings four times, No. 2 three times (the last at age 39) and No. 3 once. Jones finished second twice at Boston and once at New York and Chicago. She had five sub-2:30 races, although all five carry an asterisk for having come on courses considered point-to-point.

7. Desiree Davila – At 28, she is on the cusp of greatness. Fastest U.S. marathoner of 2010. Aided by a tailwind and fueled by her determination to win, Davila ran 2:22:38 at Boston in 2011, losing by two seconds but becoming the third fastest U.S. woman under any conditions. Also had a solid 11th place at the 2009 Berlin worlds. Her last three marathons all have been sub-2:30.

8. Kara Goucher. Made a stunning marathon debut at New York in 2008, with her third-place time of 2:25:53 the fastest by a U.S. woman debutante. Leading U.S. finisher at the 2009 worlds (10th in 2:27:48). Third at Boston in 2009, fifth last year in her first marathon after giving birth to a son.

9. Patti Catalano. In 1981, Sports Illustrated called her the world’s No. 2 marathoner at that time (behind Grete Waitz). A fierce competitor, she was the dominant U.S. woman of the late 1970s. The oft-injured Catalano won the Honolulu Marathon several times and finished second at Boston three times.

10. Colleen De Reuck. One week before her 40th birthday and four years after becoming a U.S. citizen, the South Africa native won the 2004 U.S. Olympic trials. DeReuck, now 47, plans to run the trials again Saturday – and she comes into the race as the No. 8 performer based on times the past two seasons, with a best of 2:30:51. Has three times under 2:29 as a U.S. runner, including 2:28:25 at the 2004 trials. Finished 39th in the Athens Games – her third Olympic marathon appearance.